1970 Road Runner with bone-stock NOS restored & rebuilt 383.

Story time: Cruising around town, car dies at intersection while idling at red light. I'm suspecting vapor lock so I push it out of the way and wait till it cools off. Car restarts and I'm on my way. Does it again a couple blocks down. This time takes more patience to restart. I'm done, take the freeway back home. Car dies at 75mph, coast it to my exit. Starts again for one last time and dies two blocks down. Next morning, I crank it and no-go.

What I've checked:
Carb gets fuel.
Ballast has resistance and I've even swapped it with my Coronet.
Electronic Ignition box is good, swapped it as well, no-go.
Coil is good and gets voltage, swapped it with both an ACCEL coil and the stock one in the Coronet, both are not outputting a spark.
Distributor pick-up makes good contact.
Wiring is mint and tight everywhere.
No blown fuses.
Cleaned up all the ground connections.
Battery is brand new and making good contact.

At this point, I have no clue what on Earth is going on! Based on the story, it sounds like a progressive failure. Not instant death of a part or something...

When doing all the testing / key on / cranking last night, I've noticed the alternator was pretty warm. Decided to try and disconnect it to see if it made a difference, no-go.

 

M -

Are you sure there aren't any loose wires that should be connected to the ignition relay?

The other possibility is a stuck needle and seat on the carb.
If the bowls are flooded, it with crank but not start.

The odds are one of your test gave you a false negative.

Archer

 

Yes, I'm sure.

As I've mentioned above, no electricity is running though the spark plug wires. That's what I'm trying to figure out. Gasoline or not, it's not solving an spark issue.

 

Rotor is turning when you crank it?

 

Yup, rotor is turning.

 

Distributor magnetic pickup to reluctor out of adjustment, or magnetic pickup pooched!

 

yep

 

There's a good signal between pick-up and reluctor, and the pickup's fine. ECU is fine.

There is no spark coming out of the coil. The coil itself won't fire.

 

Seen similar / this on a friends boat with ford power. Tight bushings in distributor, overheats magnetic pickup, ignition fails. Cools off engine runs. Might be worth a try to swap out distributors?

 

Some of this might not apply, but I'll go through it anyway

ALWAYS suspect harness connectors, especially the distributor, because it's almost no current going through it. The slightest bit of loose or corrosion will "kill" the signal. Wiggle, work, inspect the connectors

Make ABsoLUTEly CERTAIN that the ECU is grounded. use star lock washers, scrape around the bolt holes

Try disconnecting a tach if you have one. Get it down to "only one wire" hooked to coil NEG.....the one going to the ECU

Check coil + voltage when it quits and or run a jumper from battery (starter relay) to coil +

Pull dist. connector. Repeatedly touch the bare harness connector while looking for a spark, One touch should give you one spark.

Examine interior of distributor, look for bent shaft, loose, strike damage to reluctor / pickup, and other rust and debri. Obtain a .008 inch BRASS feeler gauge. O'Reallys did have these. Set the reluctor gap.

Hook your multimeter to the distributor connector on low AC that's right---AC volts and crank the engine. You should get about 1V generated

If you can beg or borrow another distributor, you can try it by just turning in your fingers, don't have to install it. Just hook it up, turn the key to run, and twist while looking for spark.

Coils are a crap shook. They can be good, they can heat up and die, and be bad. Might want to 'throw' another coil at it

VOLTAGE checks

With key in "run" coil+ should be below battery, perhaps 6-10V. If it's below that you have a problem, if it's clear up to "same as battery" you have a problem

Check coil NEG voltage. It should be very low, perhaps 1/2 -1 volt. Very much above that is a problem, and zero is a problem

-----------------------------------------------------

Frankly, heating up and dying sounds like coil or ECU. Since you've changed the ECU and coil..................

++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++

FIRST THING I'D DO after all you've done:

Check the connectors, and check and or change the distributor.

 

If you know the Dist is fazed and working proper....
You have juice to the coil and swapped it with another....
The ECU must be bad or you have a wiring problem....
Recheck the ECU wiring...Must have a broken wire or came loose somewhere..

 

m -
Just thinking logically.

You have power TO the coil and not power out (meaning you checked the field strength from the coil wire), and you believe the coil is fine.

One of your determinations must be incorrect.

Archer

 

You cannot make those assumptions. A bad box will allow voltage TO the coil

Check the coil NEG voltage with key on

very low voltage, IE about 1/2--1 volt means the box is conducting. This doesn't mean the box is good or bad, it means it may not be bad

If NEG coil voltage is quite high, near or "same as" battery, it means the coil is not conducting through the box. If so the box is BAD or that the box IS NOT GROUNDED

No coil voltage to coil+ means wiring problem

No coil voltage "in start" means wiring problem

Some sort of voltage at coil + but nothing at NEG means coil is open

UNHOOK anything at the coil not needed. That is, the radio condenser and the TACH.

CHECK for spark right at the coil. To do that, run a jumper to coil POS from starter relay BATT stud. This supplies good hot 12V to coil FOR CERTAIN

Jumper the starter relay to crank the engine

Use a grounded probe (screwdriver) right at the coil tower to check for spark.

 

Everything is "good", not much info for diagnostic help.

How about Battery volts, ballast volts in and out key run and start.

Coil + volts key run and start.

Checked at battery negative and at block.

Specifics would help.

 

After extensive tests this week-end, everything check out fine and has been singled out to the ECU giving out.

The reason I suspect the swap didn't work with the one from my Coronet, is that the Coronet is a 5-prong at the ECU and a 4-prong at the ballast. The Road Runner is 4-prong at the ECU and 2-prong at the ballast. I've ordered this replacement (same part #) and we'll see if that fixes it.

 

The only time I had problems with starting my 318 was the dist pickup.. Look under the pickup on the advance plate = look for a drop of wax ?? Buy a good NAPA one ? Autozone sucks big time for electronics

 

New ECU arrived today, the car fired right up.

Makes me wonder how a brand new box got toast so fast. I suspect my tachometer electronics might be feeding/jumping voltage over to the negative coil, slowing messing with the ECU?

 

Glad you got it Running with the New ECU....

 

I doubt it. One huge factor "today" is simply quality and quality control. make DARN certain the box is grounded

 

Agreed !!!!!!!!!!!!!